Catalysis And Elementary Enzyme Reactions

Let’s evaluate each of the options based on the properties of catalysts:
- Option (1): "Catalyst is required in large quantities to catalyse reactions." This statement is incorrect. Catalysts are used in very small amounts because they are not consumed in the reaction. They lower the activation energy and speed up the reaction without being used up.
- Option (2): "Same reactants may give different products by using different catalysts." This statement is correct. Different catalysts can direct the reaction towards different products by providing an alternative reaction pathway with a different mechanism. For example, in hydrogenation of alkenes, different metal catalysts like Ni, Pt, or Pd can give different selectivity towards the product.
- Option (3): "Catalytic activity of catalyst does not depend upon the strength of chemisorption." This statement is incorrect. The catalytic activity of many catalysts (especially solid catalysts) does indeed depend on the strength of chemisorption (adsorption of reactants on the catalyst surface). The right strength of chemisorption ensures proper orientation of reactants and helps facilitate the reaction.
- Option (4): "A catalyst does not remain the same before and after the reaction." This statement is incorrect. A catalyst remains chemically unchanged at the end of the reaction. It may undergo temporary changes in its physical state or chemical bonding during the reaction, but it is regenerated in its original form after the reaction.
Thus, the correct answer is Option (2). Example of Catalysis: Hydrogenation of Alkenes Let us consider the hydrogenation of an alkene (e.g., ethene) to ethane as an example of catalytic activity: In this reaction: - The reactant ethene reacts with hydrogen in the presence of a platinum (Pt) catalyst, leading to the formation of ethane. - The catalyst Pt remains unchanged at the end of the reaction but helps lower the activation energy for the hydrogenation process.

The correct option is (A) : A-II, B-IV, C-II, D-I

The correct option is (B) : Negative